#include<cmath>
using namespace std;

#define NLAYERS_BCAL 10
double BCAL_tdiff(double geometric_mean, int layer)
{
	double tw_par[NLAYERS_BCAL][7] ={
		{-1203.93, 1289.24, -565.586, 130.172, -16.5902, 1.11108, -0.0305763},	// layer 1
		{1351.39, -1165.02, 300.597, 4.71097, -14.2415, 2.23867, -0.110404},	// layer 2
		{126.923, -65.3371, 0.440411, 3.10544, 0.198477, -0.193724, 0.0181466},	// layer 3
		{-2143.04, 1217.81, -26.6048, -67.9735, -3.70158, 4.99012, -0.516172},	// layer 4
		{0, 0, 0, 0, 0, 0, 0},	// layer 5
		{0, 0, 0, 0, 0, 0, 0},	// layer 6
		{0, 0, 0, 0, 0, 0, 0},	// layer 7
		{0, 0, 0, 0, 0, 0, 0},	// layer 8
		{0, 0, 0, 0, 0, 0, 0},	// layer 9
		{0, 0, 0, 0, 0, 0, 0}	// layer 10
		};

	layer = layer<1 ? 1:layer>NLAYERS_BCAL ? NLAYERS_BCAL:layer;
	double *p = tw_par[layer-1];
	double x = log(geometric_mean);
	return p[0]+x*(p[1]+x*(p[2]+x*(p[3]+x*(p[4]+x*(p[5]+x*p[6])))));
}